VISTA —— Roman Sagan and Art Konold are coworkers who have a lot in common —— both are letter carriers for the Vista Post Office, both are married with two children, both are likeable middle-aged guys with laid-back smiles.

But Konold is healthy and Sagan is sick with a congenital disease that has destroyed his kidneys. For the past 18 months, he has undergone painful dialysis treatments three times a week while he waits for a life-saving transplant. To Konold, that just didn't seem right.

On Wednesday, the wait will be over. Konold is donating a kidney to Sagan in a six-hour surgery at UCSD Medical Center.

Though the transplant has been months in the planning, no one seems more surprised than Konold, a 51-year-old vegetarian and tae kwon do instructor who has never had surgery of any kind.

"It's amazing that this has all worked out," he said Friday. "I never would have believed we would make it to this point, but I'm glad we did. I'm ready."

To Sagan, it's nothing short of a miracle.

"He's a hero," said Sagan, 46. "I don't know how to thank him for what he's doing. This really is the gift of life."

Sagan was diagnosed with kidney disease more than 12 years ago, but his condition worsened dramatically in the past few years. He continued to work, even when dialysis left him weak and exhausted.

His arms —— strong from years of hauling mail along his Vista route —— are now scarred and bruised from dialysis. There is a walnut-sized lump under his skin, where the needle is regularly inserted, that vibrates to the touch.

Last year, Sagan's friends and colleagues, long impressed by his positive outlook and stamina, began to realize dialysis was taking its toll.

"I could see that he was getting tired," Konold said. "And I kept thinking 'I wonder why no one has stepped up to help him (by donating a kidney.) Who wouldn't do that, if they knew they could?' "

In a casual conversation in October, Konold asked Sagan his blood type. When he heard it was A-positive —— the same as his own —— he volunteered to be tested as a possible donor.

"I never thought I would be a match," said Konold. "In fact, we went through a whole series of tests and each time I expected to be ruled out."

Finding an organ match is no easy feat. In addition to blood type, potential donors are tested for six genetic markers, with at least one required to make a good match. The odds drop when the donor is not a family member, or is a different ethnicity. Sagan is Filipino; Konold is white.

When doctors finally determined Konold's kidney would be compatible, it was "a shock," he said.

Doctors provided Konold and Sagan with "tons of information" about the process and Konold sat down with his family to try to explain his decision and ease any fears.

He said his wife was a little resistant.

"She couldn't believe I would want to do this," Konold said."I can't explain it, but it just made sense to me. It (the kidney) is nothing I need."

After the surgery, Sagan is expected to remain hospitalized through Sunday; Konold could be released as early as Friday. Recovery for both men is expected to take about three months.

Colleagues and supervisors at the post office annex on East Vista Way have been nothing but supportive, the two men said.

"It's going to be rough on them, with both of us out for a while," Sagan said. "But they have been so helpful and kind."

Alfonso Foster, acting station manager at the annex, said he is proud to work with Konold and Sagan.

"I knew what (Roman) was going through and it was emotional for me to see him so ill," he said. "When Art told me about the transplant, I was so touched and so proud —— and completely ecstatic for Roman. They are both remarkable guys."

Sagan said he will never forget what Konold is giving him.

"We will have this bond for the rest of our lives," he said.